1. Field of the Invention
The invention relates to a semiconductor light-emitting device. More particularly, the invention relates to a vertical semiconductor light-emitting device.
2. Description of Related Art
In recent years, luminescence efficiency of light-emitting diodes (LEDs) has been continuously improved. Consequently, fluorescent lamps and incandescent bulbs are gradually replaced with LEDs in some application areas, such as scanning light sources which require high response speed, back or front light sources of liquid crystal displays (LCDs), automobile dashboard illumination, traffic signs, and general illumination devices. Common LEDs are usually semiconductor devices which are made of III-V group compounds, such as GaP, GaAs, and so on. Basically, the LED converts electric energy into light. Specifically, an electric current is applied to the aforesaid semiconductor compound and, through the combination of electrons and holes, excessive energy can be released in the form of light.
FIG. 1 is a schematic cross-sectional view illustrating a conventional LED chip. With reference to FIG. 1, the LED chip 200 includes a light-emitting structure layer 110, a bonding layer 120, a conductive substrate 130, an n-type electrode 142, a p-type electrode 144, a metallic reflective layer 250, and a transparent conductive layer 260. The light-emitting structure layer 110 is configured on the conductive substrate 130, and the bonding layer 120 is located between the light-emitting structure layer 110 and the conductive substrate 130. The light-emitting structure layer 110 has a p-type semiconductor layer 112, an n-type semiconductor layer 114, and an active layer 116 located between the p-type semiconductor layer 112 and the n-type semiconductor layer 114. The n-type electrode 142 is configured on a surface of the n-type semiconductor layer 114 away from the light-emitting structure layer 110, and the p-type electrode 144 is configured on a surface of the conductive substrate 130 away from the light-emitting structure layer 110. The metallic reflective layer 250 is configured between the bonding layer 120 and the light-emitting structure layer 110, and the transparent conductive layer 260 is configured between the metallic reflective layer 250 and the light-emitting structure layer 110. That is to say, the LED chip 200 not only includes the light-emitting structure layer 110, the bonding layer 120, the conductive substrate 130, the electrode 142, the electrode 144, and the metallic reflective layer 250 but also includes the transparent conductive layer 260 configured between the metallic reflective layer 250 and the light-emitting structure layer 110.
In the LED chip 200, the metallic reflective layer 250 has the light reflection properties, while the transparent conductive layer 260 has the ohmic conductive properties. However, during fabrication of the LED chip 200, heat treatment is required, which is likely to cause mutual diffusion between the transparent conductive layer 260 and the metallic reflective layer 250. Thereby, the metallic reflective layer 250 is atomized during fabrication of the LED chip 200, reflectivity of the metallic reflective layer 250 is reduced, and luminance efficiency of the LED chip 200 is deteriorated.